1. Field of the Invention
The present invention relates to a device for inducing compression in a cell culture, more particularly, to a sample support which is fixed to a flexible membrane, where, upon movement of the flexible membrane, the sample support is compressed against a stop thereby compressing a cell culture retained on the support.
2. Prior Art
Culturing cells in vitro for subsequent implantation in a patient is an emerging area in medicine. Presently, cells such as cartilage cells are cultured by removing a piece of articular cartilage from a healthy section of the knee, isolating chondrocytes, increasing the number of chondrocytes in culture and implanting the cells into a defect in a patient's cartilage. A drawback to this method of implanting cultured cells into a patient's cartilage is that the cartilage that forms in vivo has less than 30% of the biomechanical strength of normal cartilage cells.
Therefore, a need has arisen to develop a device for culturing cells in vitro including cartilage tissue that can yield cells and a matrix which have sufficient material strength to withstand rigorous use in joints such as the knee or other biomechanically active environments that subject cells to compressive loads. Present tissue engineering techniques so far have been unable to produce such cells and matrix which can withstand compressive loads. For example, one method that has been used to cultivate cartilage cells in an environment to simulate the native dynamic state of repeated compressive loads is to culture the cells within a metal cylinder. A metal piston received within the cylinder is driven to induce a compressive load upon the cells during culturing in confined or unconfined compression. However, this method of using metallic piston in cylinder components to provide compression to cells and tissues grown in vitro still does not sufficiently mimic the native environment. The volume of the bathing medium is usually insufficient to sustain cells for a long period, there is difficulty in adding or removing medium and it is difficult to optically examine the sample during dynamic compression. Hence, the cells cultured thereby do not possess the required biomechanical strength of native tissue.
Another approach to applying compressive loads to cartilage is that of applying hydraulic pressure to cells or tissue confined in a tube. A nutrative medium is pumped into a three-dimensional construct populated with cells that is confined in a tube or cylinder in line with the pump. The flowing medium provides nutrition, but also adds fluid sheer stress as well as compression to the matrix and cells. However, the upstream fluid flow side of the sample will be subjected to greater pressure than the downstream side. Hence, a non-hydrogenous pressure gradient will occur throughout the sample. There is also difficulty in sustaining flow through the sample as cells divide, produce a matrix and fill in the interstices of the support matrix. Eventually, the fluid pressure will of necessity be quite high in order to provide nutrition to cells. In this case, cell death may occur due to excessive pressure. At this point, diffusion may be the principle means by which nutrition is provided to cells in the three-dimensional matrix.
Accordingly, a need remains for a device which cultures cells under compressive loads either for implant into a patient and/or for studying the impact of compressive load placement upon cell cultures, is user friendly, easily sterilized, allows for ease of sample loading, mechanical loading, addition and removal of nutrifying medium, addition of bioactive agents and allows viewing of the samples.